Seminal Plasma, Not Cells May Be Key to HIV Transmission

MONDAY, Feb. 15 (HealthDay News) -- In HIV infection resulting from men having sex with men (MSM), the infection is likely transmitted via HIV RNA in the plasma constituent of semen, not by the HIV DNA located in seminal cells, according to a study in the Feb. 10 issue of Science Translational Medicine.

David M. Butler, M.D., of the University of California in San Diego, and colleagues collected samples of urine, blood and semen from six males with HIV infection and recent male sex partners. The seminal plasma and seminal cells were separated by centrifuge. The HIV RNA from the blood of both partners and from the seminal plasma of the HIV source partners was extracted, and the HIV DNA was extracted from the HIV source partners' infected seminal cells. The HIV RNA from the blood of both partners and the HIV RNA and HIV DNA from the semen of the HIV source partners were sequenced, and the origin of the transmitted HIV was inferred from phylogenetic and population genetic analysis.

The researchers found that for all six partner pairs, viral sequences derived from the recipient partner's blood plasma clustered with the sequences from the source partner's seminal plasma, not the seminal cells, indicating that the HIV originated in seminal plasma rather than in seminal cells.

"Our results provide the most compelling experimental confirmation for the hypothesis that cell-free HIV RNA in seminal plasma, and not cell-associated HIV DNA in seminal cells, is the origin of sexually transmitted virus between MSM," the authors write.